What happens when an empty variable is exported

So for example I have this:

Code:

---

ifeq "$(PWD)" ""
uname_s:=WIN32
_WIN32:=1

uname_p:=$(or $(PROCESSOR_ARCHITEW6432),$(PROCESSOR_ARCHITECTURE))
AMD64:=$(if $(filter AMD64,$(uname_p)),1)
x86:=$(if $(filter x86,$(uname_p)),1)

cpu_sfx:=$(if $(is_amd64),.amd64.,.)
else
uname_s:=$(shell uname -s)
LINUX:=$(if $(filter Linux,$(uname_s)),1)
OSX:=$(if $(filter Darwin,$(uname_s)),1)

uname_p:=$(shell uname -p)
AMD64:=$(if $(filter AMD64 x86_64,$(uname_p)),1)
IA32:=$(if $(filter %86,$(uname_p)),1)
ARM:=$(if $(filter arm%,$(uname_p)),1)

cpu_sfx:=$(or $(if $(is_arm),.arm.),$(if $(is_amd),.amd64.))
cpu_sfx:=$(or $(cpu_sfx),$(if $(i32),.ia32.,.))
endif
...
export PATH
export _DEBUG
export TOP_DIR
export LIBRARY_PATH

export _WIN32
export LINUX
export OSX
export AMD64
export x86
export IA32
export ARM
...

---

Do the variables get defined anyways or are they skipped? Asking because I want to know the result of for example

Code:

---

#ifdef _WIN32

---

when _WIN32 was empty, I never tried before and since I'm still implementing some new functions I'm not gonna see the result any time soon.

Also I'm at my wits end trying to capture the output of a shell command here:

Code:

---

ifneq "$(is_gnu)" ""
StrInc="$(hash)include <$1s>" | $(CC) -c -x c -
TryInc=$(shell $(call StrInc,$1))
CanInc=$(if $(findstring error,$(call TryInc,$1)),,1)
HAVE_PTHREAD:=$(call CanInc,pthread.h)
endif

---

Would appreciate help fixing it, currently HAVE_PTHREAD should be empty because of the extra 's' I added for checking the functionality works as intended, instead I get '1' in it

Can't find, now, the actual reference on make manual, but uninitialized variables aren't exported:

Code:

---

# Makefile

#X=1
export X

all:
  make -f Makefile.2

---

Code:

---

# Makefile.2
ifdef X
  MSG=Imported
else
  MSG=Not imported
endif

all:
  @echo $(MSG)

---

Running:

Code:

---

$ make
make -f Makefile.2
make[1]: Entering directory './tmp'
Not imported
make[1]: Leaving directory './tmp'

---

Change to X=1 and it is ok.

Quote:

---

Originally Posted by flp1969

Can't find, now, the actual reference on make manual, but uninitialized variables aren't exported:

Code:

---

# Makefile

#X=1
export X

all:
  make -f Makefile.2

---

Code:

---

# Makefile.2
ifdef X
  MSG=Imported
else
  MSG=Not imported
endif

all:
  @echo $(MSG)

---

Running:

Code:

---

$ make
make -f Makefile.2
make[1]: Entering directory './tmp'
Not imported
make[1]: Leaving directory './tmp'

---

Change to X=1 and it is ok.

---

Good to know, thx